KVM: PPC: Book3S PR: Enable use on POWER9 bare-metal hosts in HPT mode

It turns out that PR KVM has no dependency on the format of HPTEs,
because it uses functions pointed to by mmu_hash_ops which do all
the formatting and interpretation of HPTEs.  Thus we can allow PR
KVM to load on POWER9 bare-metal hosts as long as they are running
in HPT mode.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>